Search found 34 matches

by Papalapa
Tue Jul 09, 2019 8:42 am
Forum: Hardware
Topic: 16k internal RAM and graphics issue (I think).
Replies: 11
Views: 839

Re: 16k internal RAM and graphics issue (I think).

Don’t bother with the 10kΩ resistor, as this is only required if you are fitting a battery back-up system [see http://www.zx81.de/english/32k-rame.htm ]. Without a battery, it serves no purpose. With modern faster SRAM chips, sometimes a control line to the SRAM chip may need a low value capacitor ...
by Papalapa
Mon Jul 08, 2019 8:44 am
Forum: Hardware
Topic: 16k internal RAM and graphics issue (I think).
Replies: 11
Views: 839

Re: 16k internal RAM and graphics issue (I think).

I have done the same MOD and even with the 10K SMD resistor I get this kind of "noise" on the pictures.

In my case the solution was to add a 68pF capacitor between the pins 20 and 22 of the IC.
by Papalapa
Mon Jul 01, 2019 12:14 pm
Forum: Hardware
Topic: Memopak 16k - in need of new caps etc. before being used?
Replies: 14
Views: 1717

Re: Memopak 16k - in need of new caps etc. before being used?

This looks like it. http://www.zx81.de/memotech/memory16.txt Many thanks Lardo, I see that in fact they are only used to set the RAMpack as master or slave. Humm.... I remember that the original XT IBM PCs also have the same DIP switches to setup the floppy drives as A or B Long time ago.... :D
by Papalapa
Sun Jun 30, 2019 11:55 am
Forum: Hardware
Topic: Memopak 16k - in need of new caps etc. before being used?
Replies: 14
Views: 1717

Re: Memopak 16k - in need of new caps etc. before being used?

I'm sorry to refloat this post after more than two years, but I have a question about the Memopak 16K What the hell are the DIP switches on the back of the module used for? I download the user manual and there's no mention on it, also I do not found any information in Internet. Anyone has some infor...
by Papalapa
Thu Jun 13, 2019 9:32 am
Forum: Hardware
Topic: White screen and no cursor at all
Replies: 38
Views: 3482

Re: White screen and no cursor at all

Well, finally I get an original C210 ULA for the second Zeddy and once installed is perfectly working.

Now is time to play with the TZXduino and the old software :D
by Papalapa
Mon Jun 10, 2019 8:45 am
Forum: Hardware
Topic: White screen and no cursor at all
Replies: 38
Views: 3482

Re: White screen and no cursor at all

Just checked my order history on Sell My Retro and it appears I have fitted 24 like this! I have not had to move R1 much from there on any of them. I believe PokeMon sets them up for one ULA type before sending them out... So you should only need to adjust them slightly if using the same ULA type. ...
by Papalapa
Sun Jun 09, 2019 11:39 am
Forum: Hardware
Topic: White screen and no cursor at all
Replies: 38
Views: 3482

Re: White screen and no cursor at all

Once you adjust the ZX8-CCB you should get a really good picture. For later ULAs I start with this position and then fine tune:- 35DC1118-6135-4F8E-B637-8CCB59040850.jpeg Yellow lines added for clarity. ;) Before adjusting I always take a photo of the current position. Very useful when it gets wors...
by Papalapa
Sun Jun 09, 2019 11:37 am
Forum: Hardware
Topic: White screen and no cursor at all
Replies: 38
Views: 3482

Re: White screen and no cursor at all

Isn't that mini-pcb supposed to go into the modulator can? :? (after you rip its contents out). That would very much tidy up the wiring since all signals / power supply you need is right there. Yeah that's right but if someday you want to go back and to get the RF signal it's easy and if do you rip...
by Papalapa
Sat Jun 08, 2019 8:13 pm
Forum: Hardware
Topic: White screen and no cursor at all
Replies: 38
Views: 3482

Re: White screen and no cursor at all

Well, finally I have located and ordered an ULA and while it arrives I made a "lifting" to ZX81 bought to @Lardo Boffin. I found a small breakage on the flat cable that goes to the keyboard that has affected 8 keys but fortunatelly a cut with the scissors has been enough to go back to the normallity...
by Papalapa
Mon Jun 03, 2019 8:49 am
Forum: SALES
Topic: ZX81 ULA
Replies: 76
Views: 21664

Re: ZX81 ULA

1024MAK wrote:
Mon Jun 03, 2019 6:37 am
If we hear a shriek of joy from Barcelona, we will know why :lol:

Mark
For sure Mark :lol: